7. Project Summary/Abstract The purpose of this work is to obtain a better understanding of the communication difficulties experienced by listeners with sensorineural hearing loss in complex, multisource acoustic environments. The basic premise upon which this research is based is that much of this difficulty is due to an interaction between peripheral hearing loss and more centrally-based processes responsible for source segregation, focused and divided attention, and working memory. On a theoretical level, our view is that the competition between sound sources may be characterized according to a distinction between two basic mechanisms of masking: energetic masking, which is primarily due to overlapping patterns of excitation in the auditory periphery; and informational masking, which results from the limitations on processing at later stages in the auditory nervous system and brain. This distinction is pervasive in auditory tasks affecting simple detection, discrimination and identification, and speech recognition. On a general level, both peripheral and central factors in masking affect the formation, maintenance, and processing of sequences of related auditory events, or streams and a theme throughout this work is to understand more fully the processing of sequential information. The approach taken here is to attempt to evaluate the influences of energetic and informational masking on performance in a variety of tasks placing demands at different levels oaf the auditory system. The long-range goal is to develop an integrated theory of auditory masking that accounts for energetic and informational masking generally and successfully predicts the consequences of cochlear hearing loss.